Complexation of small neutral organic molecules by water soluble calix[4]arenes

The inclusion of small neutral organic guests (alcohols, ketones and nitriles) by water-soluble calix[4]arene receptors was studied by 1H NMR spectroscopy at neutral pH. The guests are included into the host hydrophobic cavity by their apolar aliphatic residues. The binding constants, determined by 1H NMR titrations, confirm the importance of charge assistance in the apolar binding of guests inside calixarene cavities and highlight the role played by the conformational properties of the receptors in the recognition process.